Dextroy Dublin got off the R train ready for playoff soccer. The problem: There was no field – or school for that matter – in sight as the Thomas Jefferson midfielder walked along 46th street in Midtown Manhattan.

He had the wrong 46th street – the game was at William Bryant in Astoria.

“I felt lost – like a little boy in the big city,” said the sophomore, who came to New York from Guyana a little over a year ago. “I didn’t know where I was going.”

Bryant wished he never found its school.

After sitting much of the first half for arriving late, Dublin scored once and assisted on the game-winning tally, leading the 19th-seeded Orange Wave to a 2-1 upset of No. 14 Bryant in the opening round of the PSAL Class A playoffs. Jefferson, which trailed by a goal at halftime, will take on defending city champion Beacon, the third overall seed, on Thursday at 3:30 p.m. in the second round.

“At halftime our coach said we have to win this game or we’re going home,” Jefferson keeper Trevor Tucker said. “We’re not ready to go home yet.”

Dublin beat a host of Owls defenders on a run down the right flank before sneaking a near side shot past Bryant keeper Ante Lonic to get the Orange Wave (8-3-2) even in the 52nd minute. Four minutes before the end of regulation, he used his speed to turn the corner by the end line, drew Lonic off his line and fed Antoneil Sismon for the uncontested game-winning tap-in.

“They couldn’t match my speed, and there’s a lot more of that,” he said, smiling broadly.

Jefferson has enjoyed somewhat surprising success in its first season in the ‘A’ league. It graduated 14 seniors from last year’s club, which earned a share of the Brooklyn B South crown and reached the PSAL Class B quarterfinals.

Yet coach Frank Nicholas’ squad finished second in Brooklyn A Central, behind undefeated Tilden, and went on the road in the first round and beat Bryant, a quarterfinalist last fall, despite the absence of keeper Andrew Vargas, who moved to Florida with his family. In his place, Tucker did a fine job keeping Bryant at the one goal until Dublin’s explosion.

“If you look at us, we’ve come back a lot,” Nicholas said. “These kids put their hearts into it. They keep doing it time and time again. For me, I’m so happy right now. I never thought we would get this far.”

Bryant struck first, 11 minutes in, when Andres Sung scored from inside the penalty area. The match took a wrong turn for the Owls in the 21st minute, when star midfielder Annes Salkovic collided with a Jefferson defender, opening a cut on his head. He walked off under his own power, but was taken by an ambulance to a nearby hospital to get stitches for the wound.

The Owls (7-3-3) still had plenty of chances in the second half, but either failed to execute the final touch or their shots were off target.

“They were hungrier than we were,” Bryant coach Byron Ortiz said. “We had ample opportunities to score, but they were more energetic.”

Jefferson, meanwhile, converted on its chances, taking advantage of Dublin’s speed. At the final horn, many of its players did flips to celebrate the victory. Dublin, the player most responsible for the thrilling win, wasn’t one of them.